b-Value Distribution as an Influential AE Parametric Analysis in Damage Evaluation of Structural Material

摘要

The distribution of b-value is widely defined as the slope of the logarithmic linear frequency magnitude distribution of acoustic emission (AE) events. Largenumber of AE events with varying amplitudes are generated in brittle failure of structural materials. A consequent method of describing the distributioncharacteristics of amplitudes is emphasized by describing their b-values. Conventionally, the b-value of AE is computed by using the methods adopted inseismology, since, many similarities exist between AE and seismic waves. The b-value is usually obtained either from the cumulative frequency distributionor the discrete frequency distribution of earthquake magnitudes and the same principles hold good for the AE data analysis in material damage evaluationalso. Therefore, b-value characterized by the Gutenberg and Richter’s relations have been investigated according to the Aki’s modification for AE eventsgenerated in material cracks or crack propagations towards final damage of structural materials in the present research. The proposed maximum likelihoodmethod of Aki for calculating b-values have been applied from AE maximum amplitude distribution for acquired AE events during the crack damageexperiments in tensile loading to ductile iron (pearlite). The same method of b-value distribution has been applied to the same material for fatigue loading tocharacterize the influence of b-value distribution in evaluation of damage behaviour of pearlite structural material. The calculations show good evidenceabout crack initiation, propagation and damage phenomena by comparing with microstructural video and replica data as well.